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DR Series Best Practice Guide
16
Network Interface Card Bonding
Network interface card (NIC) bonding provides additional throughput and/or failover functionality in
the event a link is lost. The DR4100 supports two bonding modes: dynamic link aggregation and
adaptive load balancing (802.3ad and ALB). Each of these modes has their own advantages and
disadvantages that should be considered before choosing a mode.
Dynamic link aggregation (Mode 4 or 802.3ad) creates aggregation groups that utilize the same speed
and duplex (i.e. 10GB and 10GB full-duplex links). Mode 4 ( See Figure 1 ) is highly beneficial in
increasing speed and bandwidth capability for multiple data streams, but will not increase the speed
or bandwidth capability of a single data stream. Slave selection for outgoing traffic is executed
according to a simple XOR policy. When utilizing mode 4 it is important to note that the maximum
bandwidth available is not always equal to the sum of each link in the bond. Also, always ensure that
the switch(s) being used support 802.3ad Dynamic link.
Dynamic link aggregation
Adaptive load balancing (Mode 6 or ALB), the default load balancing mode, is transmit load balancing
with the addition of receive load balancing ( See figure 2 ). The receive load balancing uses address
resolution protocol (ARP) to intercept packets and reassign destination MAC addresses. This means
that traffic is distributed across slave NICs according to current load. In this mode, it is not possible to
mix interfaces of different speeds. (i.e. 10GB and 1GB links) and no specialized switch support is
required. When utilizing mode 6, the total available bandwidth of the bond is equal to the bandwidth
of a single physical connection.
When ALB is used with multiple switches, spanning tree issues can arise. Consideration of one of the
following may be needed: